Magnet control.



A. D. CARDWELL.

MAGNET CONTROL.

APPLICATION FILED NOV.16. 19m.

1,279,653. PatentedSept. 24,1918.

3 SHEETS-SHEET 1.

W m 96m A. D. CARDWELL.

MAGNET CONTROL.

APPLICATIONHLED NOV. 16, 1914.

Patented Sept. 24, 1918.

3 SHEETSSHEET 2.

QwHme/weq A. 0. CAR DWELL.

MAGNET CONTROL. APPLICATION FILED NOV. 16, [914- 1 ,279,653 PatentedSept. 24, 1918.

3 SHEETS-SHEET 3- ,UNITED STATES PATENT OFFICE.

ALLEN D. CARDWELL, OF NEW YORK, N. Y.

MAGNET CONTROL.

To all whom it may concern:

Be it known that I, ALLEN D. CARnwELL, a citizen of the United States,and a resident of the city of New York, county of Kings, and State ofNew York have invented new and useful Improvements in Magnet Controls,of which the following is a specificatiom I Y The general object of myinvention is to provide means by which the various operations of anelectromagnet may be controlled with respect to the time at which orduring which these operations are performed.

More particularly, the objects of my invention contemplate theconnection of the electromagnet in circuit with auxiliary apparatus suchas inductances, capacities and resistances, to effect the control of themagnet in various ways, for instance, to vary the rate of magnetizationof the magnet; to vary its rate of demagnetization, or both its rate ofmagnetization and demagnetization; to control, vary and maintain theperiodicity of the energization of a magnet when the magnet isperiodically energized from some source of power; to provide anarrangement whereby, when the magnet is periodically energized, energymay be stored during one period of energization, for use during asubsequent period, to control, vary or maintain the periodicity at thattime; when the magnet is periodically energized for a group of cyles ofits operation, to control the time of initial energization of the magnetwith respect to the time of operation of the energizing means and tothereafter control the periodicity of the subsequent energizations ofthe group, which two controls may be independent of each other, butcapable of being combined in the same apparatus.

Generally speaking, I obtain these controls by the connection of themagnet to be controlled in various circuits, which will be moreparticularly described hereafter, with inductances, capacities andresistances, or such of these as are necessary to secure the desiredresults, which inductances, capacities and resistances may be variableor fixed in value, according to the object to be attained.

A further object of my invention is the provision of a convenient formof variable inductance, which is so arranged as to be simple, compactand durable, so that it is Specification of Letters Patent.

Patented Sept. 24, 1918.

Application flied November 16, 1914. Serial N 0. 872,820.

possible to obtain therewith minute variations in inductance orimpedance by a simple manual adjustment and which, in order to effectthese results, takes advantage of the possibility of arranging magneticfields of force to act in conjunction with, or in oppositlon to, eachother.

My invention i applicable in many connections in which it is desired tocontrol the action of an electromagnet in various ways, and I do notintend to limit it to any specific uses. However, in order to illustratean operative apparatus in which my invention has found great utility, Ihave shown it in Figure 4 as being used in connection with a circuitsystem, such as is described in my application, Serial No. 860,318, forelectric controlling systems, filed Sept. 5, 191-1, and in order thatthe relation of the circuits of this application with those shown in mysaid application, Serial No. 860,318, may be easily traced, I have used,in Fig. 4, reference characters corresponding to those of Fig. l of myaforesaid application.

In the drawings, Figs. 1 and 2, and also Fig. 3, are simplified diagramsof connection illustrating some of the controls obtainable by myinvention in an elementary way;

Fig. 4: is a a diagram of connections showing my invention applied to asystem such as illustrated in my said application, Serial' No. 860,318;

Fig. 5 is a side view of my improved variable inductance device;

Fig. 6 is a plan view thereof;

Fig. 7 is a plan view thereof with the cover plate removed; and

Fig. 8 is a sectional plan View of a portion of Fig. 5, illustratingvarying positions of its elements.

Similar reference numerals indicate corresponding parts in the severaldrawings.

Fig. 1 illustrates means by which the rate of magnetization of anelectromagnet may be varied, and thus the time within which the magnetshall reach its maximum magnetization. The rapidity with which themagnet attracts its armature may thus be controlled. In Fig. 1, I haveshown an electromagnet 22, energized by a battery 58, and connected inseries therewith through a switch S, armature 22 of the electromagnetand contact 32. Connected in series with the electromagnet 22 is thevariable inductance 60, which is grounded, as is the battery 58, to

complete the circuit. Any other suitable connection, however, may beused instead of the ground. The inductance elements of the variableinductance 60, are preferably wound upon cores of magnetic material, toincrease the field set up by the passage of current through the coils.

Contact 32 is normally closed by a spring or equivalent means orarmature 22. When switch S is closed, a path is established for thecurrent from the battery 58 to the coils of the electromagnet 22, thencethrough variable inductance 60 to the ground. The magnetizing currentdoes not, of course, reach its maximum value instantaneously and, therise of this current from zero to maximum will set up in inductance 60 acounter-electromotive force of self-induction, which opposes the flow ofcurrent in the circuit.

Upon the breaking of the contact 32, by the movement of armature 22, thecurrent in the circuit will again fall to zero, which change of currentfrom maximum to zero.

will set up in variable inductance 60 an electromotive force due toself-induction, in the same direction as that previously taken by thebattery current. This electromotive force so set up, however, producesno current flow in a circuit, except while contact 32 is breaking, suchas that illustrated in Fig. 1, since no path is provided for it Bytaking advantage of these phenomena, I am enabled, in an arrangementsuch as that of Fig. 1, to vary the rate of magnetization of magnet 22,by increasing or decreasin the inductance and, consequently, the impeance of variable inductance 60, which may be conveniently done in themanner pointed out hereafter, thus causing the magnetism inelectromagnet 22, to build up more or less rapidly. Furthermore, in suchan arrangement I can control the rate of magnetization without at thesame time aflecting the rate of demagnetization since, While animpedance is offered to the magnetizing current, the decrease of currentfrom maximum to zero remains substantially unafi'ected.

Fig. 2 illustrates an arrangement in which both the rate ofmagnetization and of demagnetization may be varied. This arrangement,however, is capable, by slight alteration, of controlling the rateofdemagnetization only. Fig. 2 shows a battery 58, connected throughswitch S, and a resistance 23 to the armature 22*, which is normallyheld so as to close contact 32. In this case, the variable inductance 60is connected in shunt with the magnet 22, instead of in seriestherewith, as shown in Fig. 1.

Upon the closing of switch S, (contact 32 being closed), the magnetizingcurrent passes through the conductor to electromagnet 22,and also tovariable inductance 60. It is for the purpose of efiecting this divisionof current and reduction of potential that resistance 23 is included incircuit, since, were it omitted, the difference of potential across theterminals of the electromagnet would always be the same as that acrossthe battery terminals.

With resistance 23 included in the circuit, however, the current dividesas inclicated by arrows A, part of it going through the electromagnet22, and part of it through the variable inductance 60. By varying theinductance 60, I am thus enabled to impede, to a greater or less extent,the current flowing in the shunt circuit which includes variableinductance 60, while this current is increasing in value, viz.: the timeduring which the magnetism is being built up in electromagnet 22. As aresult of impeding the current in the shunt circuit, which includesvariable inductance 60, to a greater or less extent, the current isvaried in the circuit passing through the electromagnet 22, while themagnetization is being built up, and the rate of magnetization may thusbe controlled.

For varying the rate of demagnetization, which may be accomplished bythe arrangement of Fig. 2, as pointed out above, resistance 23 is notnecessary, although its inclusion in the circuit does not affect theperformance of this function.

Assuming the circuit to be broken at contact 32 by the movement ofarmature 22, a decrease in current will set up, in both theelectromagnet 22 and in the variable inductance 60, electromotive forcesby reason of their respective self-inductions, which electromotiveforces will tend to cause currents to flow in the same direction as thattaken by the battery current before the interruption of the circuit.Thus, as the battery current previously flowed in the direction of thearrows AA, the current set up by the self-induction of the electromagnet22 will flow in the direction of the arrows B-B, and that set up by theself-induction of the variable inductance 60 will flow in the directionof the arrows marked CC a path having been provided for each of thesecurrents of selfinduction.

Since these electromotive forces of self-induction oppose one another, acurrent of greater or less magnitude may be caused to flow in eitherdirection, depending upon the relative values of the self-inductions ofthe magnet 22'and variable inductance 60.

Thus, if the adjustment is such that the electromagnet 22 has thegreater self-induction, a current will be set up in the direction of thearrows B-B, the flow of which will be opposed, to greater or less extentby the electromotive force of self-induction generated 'by variableinductance 60. The rate of demagnetization of electromagnet 22 may thusbe varied by varying the inductance of variable inductance 60, since itsrate of demagnetization depends upon the relative values of theelectromotive forces of self-induction enerated in electromagnet 22 andin variable inductance 60. Thus, as the electromotive force ofself-induction of variable induotance increases, the opposition to theflow of current, (due to self-induction of electromagnet 22) increasesand demagnetization of the magnet is more rapidly effected.

If the value of the self-induction of variable inductance 60 is greaterthan that of electromagnet 22, a current will flow in the direction ofthe arrows CO, thus tending to neutralize any magnetizing current whichmay tend to exist in electro-magnet 22, and to thus still furtherincrease the rate of demagnetization of the magnet.

In the arrangements of Figs. 1 and 2, I have shown means for controllingone cycle of operations of the magnet by controlling constituentoperations of that cycle, thus ena bling me to vary the time of a cycleof operations of the magnet by varying either the time of magnetizationor the time of demagnetization, or both.

In Fig. 3, however, I have illustrated means whereby I am enabled tocontrol not only the time of one cycle of operations by controllingconstituent operations of the cycle, but the periodicity of a group ofcycles of operation, assuming the magnet to be periodically energized.By the term cycle of operations of the magnet I mean to include amagnetizing period and a demagnetizing period.

In Fig. 3, I have shown the battery 58 connected through the switch Sand resistance 23 to the armature 22*, which normally holds contact 32closed, thus permitting current to flow to the electromganet 22, as inthe previous figures. Connected in shunt with electromagnet 22, Iconnect the variable inductance 60 and a capacity C, which may or maynot be variable.

By means of capacity C, variable inductance 60 and electromagnet 22(which niay be considered as an inductance), I establish an oscillatorycircuit which includes electromagnet 22. This circuit should havesubstantially the periodicity of the energizing means, or that of amultiple of this periodicity. The periodicity of the energizing meansdepends to some extent upon a number of factors, such as the voltage ofthe battery, the value of the resistance 23, the inertia and momentum ofthe armature, and the tension of its operating spring. These factors maydiffer widely, depending upon the particular means-used to energize themagnet, and the characteristics of its component elements, or otherfactors may cause variation.

The rate of magnetization and demagnetization of electromagnet 22 may bevaried within limits in the same manner as described within reference toFig. 2.

decrease in the average periodicity throughout the group of operationsof electromagnet 22 might be caused, for instance, by some mechanicalderangement of the energizing means, say a sticking of the contacts, an1ncrease'of friction, or other cause, during certain of the cycles ofthe group, thus causing a lag in the operation of electromagnet 22.. Onthe other hand, an increase in the average periodicity throughout thegroup might also be produced by some change in condition, say anincrease in battery voltage, or other cause, afleoting certain cycles ofthe group.

It is, therefore, apparent that if the aver- 2 age periodicitythroughout the group is to be maintained constant, energy .must befurnished to the electromagnet 22 to overcome a tendency to decrease theperiodicity, and taken from electromagnet 22 to neutralize the causetending to increase the average periodicity. In an oscillatory circuit,such as that including the magnet 22, variable inductance 60 and thecondenser C, there is, as is well known, an interchange of energybetween the inductance and the capacity, which interchange takes placeat the periodicity of the circuit. Thus, the strength of electromagnet22 is added to, or subtracted from, at a rate governed by theperiodicity of the oscillatory circuit. If, therefore, the periodicityof the energizing means should tend to depart from its original valuewhich, as I have stated, should be substantially equal to theperiodicity of the oscillatory circuit, or a factor thereof, energy willbe furnished to, or taken from, electromagnet 22, thus tending torestore it to its proper periodicity.

Assuming the energizing means to tend to retard and to cause theenergization of the magnet to take place at a later time, the condenserwill discharge current into the electromagnet 22, thus momentarilyincreasing the magnetizing current and the enerpolnt of maximummagnetization to be reached more slowly.

In an apparatus such as that disclosed in Fig. 3, wherein the system issupplied with energy at each operation of the energizing means, maximumpower for controlling purposes will always :be available, since it willbe understood that if the oscillatory circuit were not supplied withenergy, there would be surges of energy between the capacity andinductances which would constantly diminish in force until the energywas entirely dissipated.

The action of my apparatus is, therefore, to some extent, that of abalance wheel, which acts to supply or abstract energy as and whenneeded, to eti'ectconstant periodicity of action.

By varying the value of the inductance of variable inductance (it), I amnot only enabled to change the periodicity of the oscillatory circuit tocompensate for changes in the factors controlling the periodicity of theenergizing means, but the periodicity of the oscillatory circuit may beimposed upon the energizing means to thus modify the periodicity of thelatter to a considerable degree.

In Fig. 4, I have shown the apparatus of Figs. 1 and 3. applied to theCil'C-tlltshown in Fig. 1, of my said application, Serial No. 860.318.wherein the magnet 22 controls the rotation of a shaft, shown at 21.

In Fig. -1, the setting in operation of magnet 22 is etfected by closingthe contact (5,

thus causing the current from battery 58 to flow through contact (3,resistance 59, armature i9, contact 56, variable inductance (30 contact32, electromagnet 22 to the ground at- 61. This causes the initialenergization of magnet '22. This first impulse is controlled withrespect to the time of closure of contact 6, by means of variableinductance as pointed out with reference to Fig. 1. The time ofmagnetization and demagnetization of magnet 22 may be controlled, tosome extent, by variable inductance 60 and capacity C, during thisstarting operation.

The magnet 2'2 having been set into operation. causes the closure ofcontact -17, under the control of cam 31, thereby establishing a circuitfrom battery 58, through relay 9, contact 47, contact 32, magnet 22, toground at 61. The energization of relay t9 causes the starting circuitto be broken at 56, so that the latter no longer has any effect. Aholding circuit is at the same time established through armature 49,contact 62, relay 49, resistance 61 to ground at 63.

From this time on, throughout the time that magnet 22 is periodicallyenergized, the periodicity of the energizatien of magnet 22 may becontrolled and varied by variable inductance 60 and condenser C, in themanner pointed out in describing Fig. 3. In the oscillatory circuit Ihave shown, in Fig. 4 I have illustrated a resistance R, for the purposeof limiting the mount of energy available for control. In practice, I

' find it best to have as large as possible an amount of energyavailable for this purpose, and preferably an amount of energy' whichapproximates the amount necessary to operate magnet 22.

The variable inductance used in connection with the circuits abovedescribed may take any convenient form. A form wlnch I have found tohave many advantages in actual practice is that illustrated in Figs.

5, (3, 7 and 8.

Referring to Fig. 5, I have shown my improved variable inductance asconsisting of two inductance elements, each comprising a pair of coilsof insulated wire wound upon magnetic cores. The cores of inductanceelement 1, are connected by a yoke 3, and those of inductance element 2are connected by a yoke 1. to a plate 5, which may rest upon and besecured to a suitable support 6. A shaft 7 is journaied in and dependsfrom plate 5, passes through an opening 3. in yoke 3, between the coils,and is secured to yoke 4;, thus supporting inductance element 2, andpermitting it to be rotated relatively to inductance element 1. mentsare preferably separated by a nonmagnetic plate 9, which is held inplace by posts, or other means, 10.

Gear 11 may be secured to shaft 7 by a screw or the like 11. At 5 is aspring washer or retarding device shown located between plate 5 and gear11 and bearing thereon with sufiicient friction or spring action toretain shaft 11 and element 2 in set position, serving also to drawshaft 11 upwardly to retain the cores of element, 2 in contact withnon-magnetic plate 9, to prevent variation of the air gap between theelements 1 and 2, said plate 9 and spring washer, also serving to steadyelement 2 and prevent chattering of the same.

Any suitable means may be provided to rotate inductance element 2, andretain it set in position as, for instance, shaft 7, provided with gearwheel 11, of relatively large diameter, which meshes with the pinion 12,carried by shaft 13, and a suitable removable finger piece, as indicatedat 15, for r0- tating shaft 13, by means of the clutch members 17thereby affording a convenient means of removing finger piece 15 if itis desired to remove cover plate 16. Pin 18 on wheel 11, and spaced pins19, 19 on plate 5 limit the rotation of gear Wheel 11 in oppositedirections.

The arrangement of the apparatus is, therefore, such that the inductanceelements may be rotated with respect to one another, so that thedirection of the magnetic flux tending to pass through the cores of oneelement may be the same as, or opposite, that; tending to pass throughthe cores of the other element. The total inductance of the apparatusintermediate these points will be determined by the characteristics. ofthe magnetic field at the point at which the apparatus is set. As shown,for the purpose of indicating to the operator the relative positions ofthe poles of the magnets, the

The yoke 3 is suitably connected The inductance ele-' gear 11 isprovided with a scale coop'erat 4 mg with an index point a, located onthe cover plate 16, and so arranged that when the zero mark is oppositethe index point a (see Fig. 6) the paths of flux of the inductanceelements will be the same, at which time the maximum impedance will beobtained and, when the numeral 100 is opposite the index point a, themagnetic fluxes will oppose one another, thus givlng the minimumimpedance. Additional means for indicating the adjustment of theinductance elements are shown in the numbers A,

on cover plate, 16, with which a pointer 15 on finger piece 15cooperates. These numbers are arranged so that a movement of the pointer15 from one of these numbers to the next produces a movement of one unitof gear wheel 11, thus providing means for more exact adjustment. Thearrangement illustrated is such that when the zero of numerals Bcoincides with the index point a, the index pointer 15 will coincidewith the upper zero of the numerals A, and when said pointer has movedin a clockwise direction to the lower zero of the numerals A the numeral10 of the index numerals B will coincide with the index point a; whenthe pointer 15 is next moved from the lower zero to the upper zero, in a.clockwise direction, the numeral 20 of the index numerals B willcoincide with the index point a, and so on alternately for each tenspaces of the index numerals B. Thus when pointer 15 is at the lowerzero, the 10, 30, 50, 7 0 and 90 numerals will coincide with index pointa, and when the pointer 15 is at the upper zero, the zero 20, 40, 60, 80and 100 of the index numerals B will coincide with the index point a.

It will be noted that the effect of my improved variable inductance islimited to the time during which the current is changing in value in thecircuit, and operates to increase the apparent resistance of thecircuit, and not its actual resistance (except by reason of such smallohmic resistance as it may have) and, therefore, does not affect themaximum power available on the line. My apparatus, therefore is of greatvalue for the regulation of telegraphic apparatus, in which the currentimpulses are necessarily minute.

While I have shown my invention in connection with various circuits, anddescribed it with relation to certain apparatus, I do not intend to beconfined to the precise details illustrated and described, as forinstance, the particular kind of electro-magnet illustrated, nor to theuse of the various controls with apparatus of any particular nature,since many changes may be made in the apparatus without departing fromthe s irit of my invention, as will be apparent to t ose skilled in theart.

What I claim is:

l. The method of varying the periodicity of cnergization of a magnetwhich consists in causing the magnet to make and breakits own circuitand imposing upon the circuit of the magnet the periodicity of anoscillatory circuit.

2. The method of varying the periodicity of energization of a magnetwhich consists 1n causing the magnet to make and break its own circuit,varying the periodicity of another circuit, and imposing the periodicityof the last named circuit upon the circuit of the magnet.

3. In an apparatus of the kind described, an electro-magnct; a circuittherefor having a contact controlled by the magnet, and a variableinductance in circuit therewith for controlling the rate ofmagnetization of said magnet.

4. In an apparatus of the kind described, an electro-magnet; a circuittherefor havin a contact controlled by the magnet, anc l means incircuit therewith for varying the rate of demagnetization of the magnet.

5. In an apparatus of the kind described, an electro-magnet; a circuittherefor having a contact controlled by the magnet, an inductance andmeans for opposing the electro-motive force of self-induction of themagnet by that of the inductance, so that the resulting current flowcontrols the rate of demagnetization of the magnet.

6. In an apparatus of the kind described, an electro-magnet; a circuittherefor having a contact controlled by the magnet, and a variableinductance in circuit therewith for controlling the rate ofdemagnetization of said magnet.

7. In an apparatus of the kind described, an electro-magnet; a circuittherefor having a contact controlled by the magnet, and means in circuittherewith for varying both, the rate of magnetization and ofdemagnetization of said magnet.

8. In an apparatus of the kind described, an electro-niagnet; a circuittherefor having a contact controlled by the magnet, a resistance in thecircuit, and a variable inductance in circuit therewith for controllingboth the rate of magnetization and of demagnetization of said magnet.

9. In an apparatus of the kind described, an electro-magnet; a circuittherefor having a contact controlled by the magnet, and a variableinductance in series therewith for controlling the rate of magnetizationof the magnet.

10. In an apparatus of the kind described, an electro-magnet; a circuittherefor having a contact controlled by the magnet and means connectedin parallel therewith for varying the rate of demagnetization of themagnet.

11. In an apparatus of the kind described,

an electro-niagnet, a circuit therefor having a contact controlled bythemagnet, a resistance in series therewith, and a variable inductancein parallel therewith for controlling the rate of magnetization of themagnet.

12. In an apparatus of the kind described, energizing means including asource of energy, an electromagnet periodically energlzed thereby, acontact in the magnet circuit controlled thereby, and means forcontrolling the periodicity of the energization of the magnet,irrespective of the energizing means.

13. In an apparatus of the kind described, energizing means including asource of energy, an electro-magnet periodically energized thereby, acontact in the magnet circuit controlled thereby, and means tending tomaintain a given periodicity of energization.

14. In an apparatus of the kind described, energizing means including asource of energy, an electro-magnet periodically energized thereby; acontact in the magnet e1rcuit controlled thereby, means for storingenergy during one period of energization for use in said magnet during asubsequent period of energization.

15. In an apparatus of the kind described, an energizing means includinga source of energy, an electro-magnet periodically energized thereby; acontact in the magnet circuit controlled thereby, and means for stor ingenergy during each period of energization for use in said magnet duringa subsequent period of energization.

16. In an apparatus of the kind described, energizing means including asource of energy and an electro-magnet periodically energized thereby;and an oscillatory circuit including said magnet, having a variableperiodicity and adapted to control the periodicity of energization ofthe magnet.

17 In an apparatus of the kind described, energizing means including asource of energy and an electro-magnet periodically energized thereby;and an oscillatory circuit including said magnet, having a variableperiodicity and adapted to control the periodicity of energization ofthe magnet by storing energy during one period of energization of themagnet for use in the magnet during a subsequent period of energization.

18. In an apparatus of the kind described, energizing means including asource of energy, an electro-magnet periodically energized thereby; andan oscillatory circuit including the magnet and having a periodicity thesame as or a multiple of the periodicity of the energizing means.

19. In an apparatus of the kind described, an electro-magnet; means forperiodically energizing said magnet, including a source of energy; acontact in the magnet circuit -an electro-magnct; means for periodicallyenergizing said magnet, including av source of energy; a contact in themagnet circuit controlled thereby,.means for initiating the energizationof said magnet; means for controlling the rate of magnetization of saidmagnet during the initial energization, and

means for controlling both the rate of magnetization and ofdemagnetization of said magnet, during the subsequent energizations,said controlling means being independent of each other.

21. In an apparatus of the kind described, an electromagnet, means forperiodically energizing said magnet, including a source of energy; acircuit for said magnet including means for initiating the energizationthereof; a variable inductance in said circuit for controlling the rateof magnetization of said magnet during the initial energization; asecond circuit for said magnet adapted to effect the subsequentenergization thereof, and a variable inductance in said second circuitfor controlling the rate of magnetization and of demagnetization of saidmagnet during such subsequent energization.

22. In an apparatus of the kind described, an electromagnet, means forperiodically energizing said magnet, including a source of energy; acircuit for said magnet includ ing means for initiating the energizationthereof; a variable inductance in said cir cuit and in series with saidmagnet for controlling the rate of magnetization of said magnet duringthe initial energization; a second circuit for said magnet adapted toeffect the subsequent energization thereof, and a variable inductance insaid second circuit and in parallel with said magnet, for controllingthe rate of magnetization and of demagnetization of said magnet duringsuch subsequent energization.

23. In an apparatus of the kind described, an electro-magnet, means forpcriodically energizing said magnet, including a source of energy; meansfor initiating the operation of the energizing means; means forcontrolling the rate of magnetization of said electromagnet during theinitial energization; and means for controlling the periodicity of thesubsequent energization of said magnet, independent of the energizingmeans.

24. In an apparatus of the kind described, an electro-magnet, means forperiodically energizing said magnet, inclnding a source of energy; meansfor initiating the operation of the energizing means; means forcontrolling the rate of magnetization of said electro-magnet during theinitial energization; and means, including a variable inductance, incircuit with the mag1 iet for controlling the periodicity of thesubsequent energization of said magnet,

independent of the energizing means.

In an apparatus of the kind described, an electro-magnet, means forpcriodically energizing said magnet, including a source of energy; meansfor initiating the operation of the energizing means; means forcontrolling the rate of magnetization of said magnet during the initialenergization; and means, including a variable inductance and a capacity,in circuit With the magnet, for controlling the periodicity of thesubsequent energization of said magnet, independent of the energizingmeans.

26. In an apparatus of the kind described, an electro-magnet, means forpcriodically energizing said magnet, includ ing a source of energy;means for initiating the operation of the energizing means; means forcontrolling the rate of magnetization of said electro-magnet during theinitial energization; and means for controlling the periodicity of thesubsequent energization of said magnet, independent of the energizingmeans, by storing energy during one period of energization of the magnetfor use in the magnet during a subsequent period of energization.

27. In an apparatus of the kind described, an electro-magnet, means forpcriodically energizing said magnet, includ ing a source of energy;means for initiating the operation of the energizing means; means forCOIltlOlling the rate of magnetization of said electro-magnet during theinitial energization; and means for controlling the periodicity of thethe subsequent energization of said magnet, independent of theenergizing means, comprisingan oscillatory circuit including said magnetand having a variable periodicity.

28. In an apparatus of the kind described, an electro-magnet, means forperiodically energizing said magnet, including a source of energy; meansfor initiating the operation of the energizing means; means forcontrolling the rate of magnetization of said electro-magnet during theinitial energization; and means for controlling the periodicity of thesubsequent energization of said magnet, independent of the energizingmeans, comprising an oscillatory circuit including the magnet and havinga periodicity the same as, or a multiple of the periodicity of theenergizing means.

In Witness whereof I have hereunto signed my name, in the presence oftwo witnesses, this 14th day of Nov., 1914.

ALLEN D. OARDWELL.

Witnesses T. F. BOURNE, MARIE F. WAINRIGHT.

